The use of laminating machines for covering paper or other discrete articles with a film barrier has been known for many years. It has become customary to laminate various types of sheet products, such as product specification sheets, menus and the like. The laminating process usually consists of feeding individual sheets through a pair of laminating rolls which receive at least one continuous supply of laminating film that is joined with the sheet at the laminating station.
One of the problems encountered in this process is accurate control of the feeding of the sheets so that they are properly joined with the laminating film and the laminating film is free of any wrinkles. Since the laminating process requires heat to join the film to the sheets, the sheets are somewhat distorted during the laminating process causing the sheets to curl in most instances.
The above-referenced application, incorporated herein by reference, discloses a laminating machine that embodies a novel feeding mechanism that readily separates individual discrete articles from a stack of articles and feeds the articles sequentially to a laminating station where a continuous supply of film is mated with the article and laminated between a heated roll and a back-up roll. A single continuous film is laminated to at least one side, and many times both sides, of the discrete articles and the discrete articles with the film adhered thereto are then redirected along an angular path, in relation to the path of entry for the discrete article, to a pair of pull rollers that are driven at a slightly greater speed than the drive roller in the laminating station to tension the laminated article at the point of contact with the drive roller and reduce the difference in compression in the fiber structure between the top and bottom surfaces of the article.
This process has been proven to reduce curling of the laminated article which inherently occurs when sufficient heat is applied in the laminating station to adhere the film to the article. The tendency for the laminated article to curl in the direction of the film side of the laminated structure is very pronounced when laminating a single film to an article, as distinguished from the simultaneously-laminating film to both sides of the article.
It has also been established that the tendency to curl in the direction of the film side of a single film laminated product becomes even more acute as the film thickness decreases and creates more of a problem when working with non-oriented plastic film.
While considerable effort has been direct toward various solutions to the curling problem, such efforts have not been totally successful in eliminating the problem. In fact, suppliers of laminating equipment are presently advising customers that certain films cannot be utilized to produce an acceptable end product because of the curling problem.